Members (Membership plugin) not showing up in e-Newsletter group

Hi, I bought e-Newsletter only because of the easy integration with the Membership plugin. I wanted to be able to send paying customers news about the site and non-paying members coupons and special offers. All non-paying customers are assigned a membership level by default by the plugin. In the members' list it says "(set by default)". I like this setup and it works for me, however none of these free members are assigned a group in e-Newsletter. Only if they are assigned a subscription upon sign up, they are added to the group. I'm not sure if this is a Membership error or a e-Newsletter error or if it's the design. According to the Membership plugin though, I've got no free users, they are not assigned a subscription, but all non-paying customers are assigned this free membership by default when their subscription ends. Can you help me with this?